This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-074846, filed Mar. 19, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a flat-panel display device in which a plurality of display pixels are arranged in a matrix, and in particular, to a flat-panel display device in which a single video signal is supplied concurrently to rows of display pixels for zoom display, for example.
A liquid crystal display device has been used in various fields as a flat-panel display device having characteristics such as lightweight, small thickness, and low power consumption. In recent years, an active matrix liquid crystal display device has come into wide use as a display for car navigation, in addition to apparatuses such as a computer, portable remote information terminal or the like.
A typical active matrix liquid crystal display device includes a liquid crystal panel and a display control unit for controlling the liquid crystal panel. The liquid crystal panel has a plurality of display pixels arranged in a matrix, a plurality of scanning lines formed along rows of the display pixels, a plurality of signal lines formed along columns of the display pixels, and a plurality of switching elements formed in the vicinity of intersections between the scanning lines and the signal lines. Each switching element is driven via the corresponding scanning line in order to apply the potential of a corresponding signal line to a corresponding display pixel. The display control unit includes a scanning line driver connected to the liquid crystal panel to drive the scanning lines, a signal line driver connected to the liquid crystal panel to drive the signal lines, and a controller for controlling operation timings for the scanning line driver and signal line driver.
By the way, the liquid crystal display device for car navigation is constructed to have a zoom display function of partially enlarging a display image. The zoom display function is obtained by simple image processing of driving a plurality of scanning lines together, and allocating a single horizontal video signal to rows of the display pixels. This image processing technique has no need of a frame memory; therefore, it is possible to reduce a manufacturing cost of the display device.
However, inventors of this application have earnestly made a research and development; as a result, in the case where the plurality of scanning lines are driven together in the active matrix liquid crystal display device, irregularity in brightness occurs between display pixels; for this reason, it has been found that the dispersion remarkably appears accompanying with a high definition of the display device.
In order to solve the conventional problem described above, an object of the present invention is to provide a flat-panel display device which can secure a preferable display quality even in the case where a plurality of scanning lines are driven together.
According to the present invention, the above object is attained by a flat-panel display device which comprises: a plurality of display pixels arranged in a matrix; a plurality of scanning lines formed along rows of the display pixels; a plurality of signal lines formed along columns of the display pixels; a plurality of switching elements formed in the vicinity of intersections between the scanning lines and the signal lines and each driven via a corresponding scanning line to apply a potential of a corresponding signal line to a corresponding display pixel; and a display control unit for driving the scanning lines and the signal lines; wherein the display control unit includes: a scanning line driver for periodically selecting at least two adjacent scanning lines from the plurality of scanning lines to drive the adjacent scanning lines together; and a scanning controller for controlling the scanning line driver to turn on the switching elements connected to a first one of the adjacent scanning lines which is located on one side of a row of the display pixels capacitively coupled thereto and driven for the row of display pixels, and the switching elements connected to a second one of the adjacent scanning lines which is located on another side of the row of display pixels capacitively coupled thereto and not driven for the row of display pixels, at a substantially identical timing, and to turn off the switching elements connected to the second adjacent scanning line at an earlier timing than that for the switching elements connected to the first adjacent scanning line by a predetermined period.
In the flat-panel display device, driving of the first adjacent scanning line and driving of the second adjacent scanning line are ended at different timings to obtain conditions which cause pixel potential levels of the display pixels to be shifted uniformly. Therefore, irregularity in brightness depending upon a difference of the shifted level amounts is prevented between the display pixels, so that a preferable display quality can be secured.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.